Tamoxifen induces eryptosis through calcium accumulation and oxidative stress

Chemotherapy-related anemia is a major obstacle in anticancer therapy. Tamoxifen (TAM) is an antiestrogen prescribed for breast cancer patients with hemolytic potential and apoptotic properties in nucleated cells. However, the eryptotic activity of TAM has hitherto escaped the efforts of investigators. RBCs from apparently healthy volunteers were treated with 1-50 μM of TAM for 24 h at 37 °C. Hemoglobin leakage and LDH, AST, and AChE activities were photometrically determined while K⁺, Na⁺, and Mg²⁺ were detected by ion-selective electrode. Flow cytometry was used to identify eryptotic cells by annexin-V-FITC, intracellular Ca²⁺ by Fluo4/AM, sell size and morphology by FSC and SSC signals, respectively, and oxidative stress by H₂DCFDA. Whole blood was also exposed to 30 μM of TAM for 24 h at 37 °C to examine the toxicity of TAM to WBCs and platelets. TAM caused Ca²⁺-independent, dose-responsive hemolysis accompanied by K⁺, LDH, and AST leakage without improving the mechanical stability of RBCs in hypotonic environments. TAM treatment also increased the proportion of cells positive for annexin-V-FITC, Fluo4, and DCF, along with diminished FSC and SSC signals and AChE activity. Notably, TAM toxicity was aggravated by sucrose but abrogated by vitamin C, PEG 8000, and urea. Moreover, TAM exhibited distinct cytotoxic profiles against leukocytes and platelets. TAM-induced eryptosis is characterized by breakdown of membrane asymmetry, inhibition of AChE activity, Ca²⁺ accumulation, cell shrinkage, and oxidative stress. Vitamin C, PEG 8000, and urea may hold promise to subvert the undesirable toxic effects of TAM on RBCs.